Composition and process for inhibiting corrosion of ferrous metal



United States Patent 3,200,071 COMPOSITION AND PROCESS FOR INHIBITINGCORROSION OF FERROUS METAL Verner L. Stromberg, Webster Groves, M0.,assignor to Petrolite Corporation, Wilmington, Del., a corporation ofDelaware No Drawing. Filed Nov. 1, 1961, Ser. No. 149,161 6 Claims. (Cl.252-8.55)

This invention relates to compositions comprising a mixture of ahydroxyaliphatic cyclic amidine, a cycloaliphatic amine and an arylsulfonic acid. This invention also relates to the use of this mixture asa corrosion inhibitor in preventing the corrosion of metals, mostparticularly iron, steel and ferrous alloys. These corrosion inhibitorsare particularly useful in preventing the corrosion of oil wellequipment, for example, in producing Wells, pipe lines, refinery storagetanks, etc. which are in contact with corrosiveoil-containing media, forexample in oil Wells producing corrosion oil or oil-brine mixtures, inrefineries, and the like.

THE HYDROXYALIPHATIC CYCLIC AMIDINE The expression cyclic amidine isemployed in its usual sense to indicate ring compounds in which thereare present either 5 or 6 members, and having 2 nitrogen whole number,for example, 1-5 or higher.

These cyclic amidines are further characterized at being substitutedimidazolines and tetrahydropyrimidines in which the two-position carbonof the ring is generally bonded to a hydrocarbon or comparable radicalderived from an acid, such as a low molal fatty acid, a high molal fattyacid, or comparable acids, polycarboxy acids, andthe like.

For details of the preparation of'imidazolines substituted in the2-position from amines, see the following U.S. patents, U.S. No.1,999,989, dated April 30, 1935, Max Bockmuhl et al., U.S. No.2,155,877, dated April 25, 1939, Edmund Waldmann et al.; and U.S. No.2,155,878, dated April 25, 1939, Edmund Waldmann et al. Also see Chem.Rev. 32, 47 (43), and Chem. Rev. 54, 593 (54).

Equally suitable for use in preparing compounds useful in our inventionand for the preparation of tetrahydropyrimidines substituted in the2-position are the corresponding polyamines containing at least oneprimary amino groupand one secondary amino group, or another primaryamino group separated from the first primary amino group by three carbonatoms instead of being separated by only 2 carbons as with imidazolines.reaction as in the case of the imidazoline is generally carried out byheating the reactants to a temperature at which 2 moles of water areevolved and ring closure is effected. For details of the preparation oftetrahydropyrimidines, see German Patent No. 700,371, dated December 18,1940, 'to Edmund Waldmann and August Chwala; Ger- This ice

man Patent No. 701,322, dated January 14, 1941, to Karl Kie-scher,Ernest Urech and Willi Klarer and U.S. Patent No. 2,194,419, dated March19, 1940, to August Chwala.

Ril-

from the acid RCOOH 131 which the 0 br the residue is part of the ring.The fatty acids employed, for example, may be saturated or unsaturated.Theymay be hydroxylated or non-hydroxylated. Branched long chain fattyacids may be employed. See I. Am. Chem. Soc. 74, 2 523 (152). Thisapplies also to the lower molecular weight acids as well. 1

Among sources of such acids may be mentioned straight chain and branchedchain, saturated and unsaturated, aliphatic, cycloaliphatic, aromatichydroaromatic, aralkyl acids, etc.- e

Examples of saturated aliphatic monocarboxylic acids comprise: acetic,propionic, butyric, valeric, caproic, heptanoic, caprylic, nonanoic,capric, undecanoic, lauric,

. tridecanoic, hyristic, pentadecanoic, palmitic, heptadecanoic,stearic, nonadecanoic, .eicosanoic, ,heneicosanoic, docosanoic,tricosanoic,tetracosanoic, PCHiBCOSaB OIC, cerotic, hepatcosanoic,montanic, nonacosanoic, melissic and' like.

Examples of ethylenic unsaturated aliphatic acids comprise: acrylic,methacrylic, crotonic, anglic, teglic, the pentenoic acids, the hexenoicacids, for example, hydrosorbic acid, the heptenoi'c acids,-the octenoicacids, the nonenoic acids, the decenoi'c acids, for example, obtusilicacid, the undecenoic acids, the dodecnenoic acids, for example,lauroleic, linderic, etc., the tridecenoic acids, the tetradecenoicacids, for example, myristoleic acid, the pentadecenoic acids, thehexadecenoic acids, for example, palmitoleic acid, the heptadecenoicacids, the octo decenoic acids, for example, petrosilenic acid, oleicacid, elidic acid, the nonadecenoic acids, for example, the eicosenoicacids, the docosenoic acids, for example, erucic acid, brassidic acid,cetoleic acid, the tetracosenic acids, and the like.

Examples of dienoic acids comprises the pentadienoic acids, thehexadienoic acids, for example, sorbic acid, the octadienoic acids, forexample, linoleic, and the like.

acid, pseudoeleostearic acid, and the like.

. Carboxylic acids containing functional groups such as hydroxy groupscan be employed. Hydroxy acids, particularly the alpha hydroxy acids,comprise glycolic acid,

lactic acid, the hydroxyvaleric acids, the hydroxy caproic acids, thehydroxyhepatonic acids, the hydroxycaprylic Modified fatty acids.

acids, the hydroxynonanoic acids, the hydroxycapric acids, thehydroxydecanoic acids, the hydroxy lauric acids, the hydroxy tridecanoicacids, the hydroxymyristic acids, the hydroxypentadecanoic acids, thehydroxy palmitic acids, the hydroxylhexadecanoic acids, thehydroxyheptadecanoic acids, the hydroxy stearic acids, the hydroxyoctadecynoic acids, for example, ricinoleic acid, ricinelaidic acid,hydroxyoctadecynoic acids, for example, ricinstearolic acid, thehydroxyeicosanoic acids, for example, hydroxyarachidic acid, thehydroxydocosanoic acids, for example, hydroxybehenic acid, and the like.

Examples of acetylated hydroxyacids comprise ricinoleyl lactic acid,acetyl ricinoleic acid, chloroacetyl ricinoleic acid, and the like.

Examples of the cyclic aliphatic carboxylic acid comprise those found inpetroleum called naphthentic acids, chaumoogric acids, cyclopentanecarboxylic acids, cyclohexanecarboxylic acid, campholic acid, fencholicacids, and the like.

Examples of aromatic monocarboxylic acids comprise benzoic acid,substituted benzoic acids, for example, the toluic acids, the xyleneoicacids, alkoxy benzoic acids, phenyl benzoic acid, naphthalene carboxylicacid, and the like.

Mixed higher fatty acidsderived from animal or vegetable sources, forexample, lard, cocoanut oil, rapeseed oil, sesame oil, palm kernel oil,palm oil, olive oil, corn oil, cottonseed oil, sardine oil, tallow,soyabean oil, peanut oil, castor oil, seal oils, whale oil, shark oil,and other fish oils, teaseed oil, partially or completely hydrogenatedanimal and vegetable oils are advantageously employed. Fatty and similaracids include those derived from the various waxes, such as beeswax,spermaceti, montan wax, Japan wax, coccerin and carnuba wax. Such acidsinclude carnaubic acid, cerotic acid, lacceric acid, montanic acid,psyllastearic acid, etc. One may also employ higher molecular weightcarboxylic acids derived by oxidation and other methods, such as fromparafiin wax, petroleum and similar hydrocarbons; resinic andhydroarornatic acids, such as hexahydrobenzoic acid, hydrogenatednaphthoic, hydrogenated carboxy diphenyl, naphthenic and abietic acid;aralkyl and aromatic acids, such as Twitchell fatty acids, napththoicacid, carboxydiphenyl pyridine carboxylic acid, blown oils, blown oilfatty acids and the like.

Other suitable acids include phenylstearic acid, benzoylnonylic acid,cetyloxybutyric acid, cetyloxyacetic acid, chlorstearic acid, etc.

Examples of the polycarboxylic acids comprise those of the aliphaticseries, for example, oxalic, malonic, succinic, glutaric, adipic,pimelic, suberic, azelaic, sebacic, nonanedicarboxylic acid,decanedicarboxylic acids, undecanedicarboxylic acids, and the like.

Examples of unsaturated aliphatic polycarboxylic acids comprise fumaric,maleic, mesoconic, citraconic, glutonic, itaconic, muconic, aconiticacids, and the like.

Examples of aromatic polycarboxylic acids comprise phathalic,isophthalic acids, terephthalie acids, substituted derivatives thereof(e.g., alkyl, chloro, alkoxy, etc. derivatives), biphenyldicarboxylicacid, diphenylether, dicarboxylic acids, diphenylsulfonedicarboxylic-acids and the like.

Higher aromatic polycarboxylic acids containing more the two carboxylicgroups comprise hemimellitic, trimellitic, trimesic, mellophanic,prehnitic, pyromellitic acids, mellitic acid, and the like.

Other polycarboxylic acids comprise the dimeric trimeric and poly acids,for example, the Emery Industries polymeric acids such as thosedescribed in US Patent 2,263,612, and the like. Other polycarboxylicacids comprise those containing ether groups, forLexample diglycollieacid. Mixtures of the above acids can be advantageously employed.

In addition, acid precursors such as esters, acid chlorides, glycerides,etc. can be employed in place of the free acid.

Hydroxy substituted irnidazolines and tetr ahydropyrimidines areobtained in the manner described above from a wide variety of polyaminescontaining hydroxy groups. Thus, Where one starts with a polyamine, forexample, a diamine of the following formula ROHCH2 where R is H or analkyl group. Among the alkylene oxides that may be employed areethylene, propylene, butylene, octylene, et-c. oxides, etc. Otheroxyalkylation agents such as glyc-ide, epichlorohydrin, etc., can beem-' ployed.

Thus, compounds, within the scope of this invention which react withpolycarboxylic acids comprise compounds of the fonmulae:

where is the residue derived from the carboxylic acid, where R 18 ahydrocarbon radical having, for example, up to about 36 carbon atomssuch as 1-36 carbon atoms, and hydrocarbons in which the carbon atomchain is interrupted by oxygen, etc, n is 2 or 3, and B is a hydrogen ora hydrocarbon radical, for example, a lower alkyl radical; and D is ahydroxy-alphat-ic radical, for example, -ROH or -R(OR'),,OH, wherein nis a Whole number, for example, 1-l0 or more but preferably 1-5 and (CBis, tor example, a divalent radical of the formula:

etc.

In general, the hydroxyalkyl cyclic amidines are prepared by reacting apoly-amine containing a terminal alkanol group with a canboxyl-ic acidattemperatures of from 150-175 C. employing an azeotroping agent such asxylene to remove water. The reaction time of '34 hours is employed.Completion of reaction is judged by the separation of 2lmoles of H .foreach canboxylic acid group. The products in general aredark viscous oil.Since the preparation of cyclic amidines is so well known" (see abovecited patents), it is not believed thatany examples are necessary toillustrate such a well known procedure; However, for purposes ofillustration the following examples are included.

' EXAMPLE 10a A solution of 1 mole of hydroxyethyl ethylene diamine,

no omon onzonmm r EXAMPLE 9b The above example is rep eated except thathydroxyethyl propylene diamine 13, 1 T

is employedin place of hydroxyethylethylene diamine and stearic acid isemployed in place of oleic acid. The prodnot is nHas EXAMPLE 40 Example10a is repeated except that floomomgomoumm (2 moles) and apolycarboxylic acid, sebacic acid (1 mole), are employed. Instead of twomoles of water being removed, as in the prior example, 4 moles of waterare removed. The product is 6 EXAMPLE 20d Example 40 is repeated with (2moles) and the polycarboxylic acid is terephthalic acid (1 mole). As inthe prior example, 4 moles of water are removed. The product is l, V V,

$a (3H2 2 H0 CHz-CHg-N N .N N-CHaCHaOH general, to .form thepolyoxyalkylated. hydroxy cyclic amidines, the hydrovxyalkylcyclicamidine is first prepared in the manner shown above and then reactedwith alkylene' oxides by the conventional manner of oxya alkylation tothe desired degree of oxyalkylation using a jacketed stainless steelautoclave in the manner described in US. Patent 2,792,369. The followingexamples are illustrative EXAMPLE 11a One mole of I l N N-omomon 3 isreacted with 1 mole of ethylene oxide at a temperature of l25130 C. anda pressure of 10-15 psi. The time regulator is set to add ethylene oxideover /2 hour followed by additional stirring for another /2 hour toinsure complete reaction. Ethylene oxide is readily taken up by 40 thereactants. The product is CH -CH N N-omomoomornofi o lnHas h EXAMPLE 12aThe above example is repeated using a propylene oxide and.

- CH: l I 1 N N'- HCH;OH

o (S11E24 under similar conditions.

The product Ja 3H2 on, 7 OH; N N+dmon o on omon a C JizHas EXAMPLE 28a uet In addition, llle cycloaliphatic group may be substituted, forexample, with a hydrocarbon group, such as an alkyl group, tor exampleH. Naphthalene 1. Naphthols J. Nap'hth ol ethers K. 'Dip'henyl L. Phenylphenols M. Diand triphenyl methanes where R is alkyl and m=05, torexample gzg ggfiigf fiiggfi Et Me, Eti

ALKYL GROUP (R) Q 1 'Methyl and ethyl e Propyl etc. (3) Butyl Althoughit is preferred that the non-cycloaliphatic (4) Amyl groups be hydrogen,other substituted groups can be em- H xyl :ployed, for example alkylgroups. p y

Thus, the term oycloaliphatic amine as employed Stra ght-chain octylherein and in the claims refers to both substituted and y 2- hy1hexy1unsubstituted cycloalipha-tic amines wherein the amino y diisobutylgroup contains at least one cycl-oal-iphatic group and the Y' remainingnitrogen valences of the amino group are saty istfied with hydrogen or asubstituted group such as alkyl. Kery1 The preferred species iscyclohexyl amine. g l g 'g l 3 3 9-118 k =1 1 traig t-c am y roxyated orunsaturated al yl, I I SULFONIO ACIDS oleyl, ric'inoleyl. These may 'beattached to one Sul-fomc acids may be described by the following forormore aromatic nuclei mula (15 Mixed alkyl from cracked .parafiin waxolefins O L (16) Mixed alkyl fro-m polymers of C -C mon'oolefins (17)Mixed tal kyl from naphthenes where n=zero or a number determined by thenumber of (13) Terpenoid, fr terpgng l fi of alcohols available hydrogengroups onthe aromatic ring QB (19) Oleic acid derivative condensates,condensed which can be substituted by R Where R is a substitutedmhr'oug'h the double bond of the 016i: chain group, preferably alkyl,and m is 1 or greater. (20) Acyl groups, i.e., alkyl aromatic ketonesusually Examples of suitable sulfonic acids are presented in made by aFrieda-Crafts acylafion reaction th following table: 21) Branched .alkylgroup derived from a ketone or Table V aldehyde AROMATIC NUCLEUS (22)Olefins from misc. synthetic processes Benzene (23) Steroid and complexal-kyl-aromatic B. Toluene Oil soluble aromatic petroleum sulfonates maybe ex- C. Xylenes, ethyl benzene, mesitylene, cymene, etc. pressed bythe .generic formula D.Phenol= I I 1' CH SCH E. Cresols, xylenols, andlower alkylated phenols (2mm) 3 F. Phenol others, anisole, pheneto'le,etc, t The following compositions are presented for purposes G. Diarylethers, dip'henyl ether, etc. of illustration and not of limitation.

Table VI Cycle-aliphatic Aromatic Sulfonic Molar Ex. (1) Cyclic Amldine(2) Amine (3) Acid gra e;

1 Iir 11 011 011 011 Oyclohexyl Amine Naphthalene Sulionic Acid 1;2;2

29 N N-CHgCHzOH Dicyclohexyl Amine Benzene Sulfonic Acid 1:1;1

3 N N CH2OH2OH Methyl Cyelohexyl Amine Toluene Sulfonie Acid 5:2;2

( T/n as 4 H0 GHQ-1 01i: 1i) III IN-CH1CH3OH Oyclohexyl AmineDodecylbenzene Sulionic Acid-. 1:3:3 A r 3 C(CH2)B -'C 5 HOCHzCHn-b'l lI 1 I--CHgCHa0H Diethyl Cyclohexyl Amine Didodecylbenzene Sulfonic 1:2:2

' Acid.

C(OH2)BC Table VI-Continued Cycloallphatic Aromatic Sulfonle Molar Ex.(1) Cyclic Amidine (2) Amine (3) Acid litstig 6e N /I\I' (CHQOHQO)ZHOyclohexyl Amine Mesitylene Sulfonic Acid 0.5:2:2

i Cn s: 1 7e N N-GHGH OH ...d Napthaleno Sulfonic Acid :53

I Cr/ aa 8e l I /II--(CH2OH20)3H do Diphenyl ether Sulfonic Acid..-1:5:5

f CHE-'33 9e I l r r-onzonion --do Napthalene Sulionic Acid 112:2

l Cu rs USE AS CORROSION INHIBITOR More specifically, this phase of theinvention relates to the inhibition of corrosion in the petroleumindustry with specific reference to producing wells, pipe lines,refineries, tank storage, etc.

The use of a corrosion inhibiting agent in the oil industry and otherindustries, and particularly for the protection of ferrous metals, iswell known. For example, see US. Patents Nos. 2,736,658, dated February28, 1954, to Pfohl et al., and 2,756,211, dated July 24, 1956, to Jones,and 2,727,003, dated December 13, 1955, to Hughes.

More specifically then, and particularly from the standpoint of oilproduction, this aspect of the invention re lates to inhibitingcorrosion caused by hydrogen sulfide, carbon dioxide, inorganic andorganic acids, combinations of each with oxygen, and with each other andoxygen. More particularly, it relates to treating wells to mitigatemetal corrosion and associated difficulties.

It should also be pointed out that the corrosiveness of oil well brineswill vary from well to well, and the proportion of corrosion inhibitingagent added to the well fluids should also be varied from well to well.Thus, in some wells it is possible to effectively control corrosion bythe addition of as little as 5 p.p.m. of our new compositions to thewell fluids, whereas in other wells, one may add 5,000-10,000 p.p.m. ormore. However, for economic consideration less than 2,000 ppm areemployed.

In using the improved compositions for protecting oil well tubing,casing and other equipment which comes in contact with the corrosiveoil-brine production, excellent results may be obtained by injecting anappropriate quantity of a selected composition into at producing well sothat it mingles with the oil-brine mixture and come into contact withthe casing, tubing, pumps and other producing equipment. One, forexample, can introduce the inhibiting composition into the top of thecasing, thus causing it to flow down into the well and thence backthrough the tubing, etc. In general, I have found that this proceduresuffices to inhibit corrosion throughout the entire system ofproduction, and collection, even including field tankage.

In case serious emulsion or gel problems are encountered, demulsifiersare advantageously added. This is important not only to avoid thetroublesome emulsions and gels themselves, but also to improve corrosioninhibition. The explanation of less effective corrosion inhibition inthe presence of emulsions apparently is that the inhibitor is somewhatsurface-active. That is, it is concentrated at interfacial surfaces.Since this surface is great in an emulsion, most of the inhibitor willbe concentrated in these interfaces and little will remain in the bodyof the oil for deposition on the metal surfaces. In many wells,oil-in-water type emulsions often occur naturally. In such wells-theinhibitors herein described tending to form water-in-oil type emulsions,often decrease the emulsion problems naturally present. Thus, inaddition to being effective corrosion inhibitors, the herein describedproducts tend to eliminate emulsion problems which sometimes appear whensome of the present day inhibitors are used in oil wells or refineryprocessing.

The method of carrying out this process is relatively simple inprinciple. The corrosion preventive reagent is dissolved in the liquidcorrosive medium in small amounts and is thus kept in contact with themetal surface to be protected. Alternatively, the corrosion inhibitormay be applied first to the metal surface, either as is, or as asolution in some carrier liquid or paste. Continuou application, as inthe corrosive solution, is the preferred method, however.

The present process finds particular utility in the protection of metalequipment of oil and gas wells, especially those containing or producingan acidic constituent *such as H 8, CO inorganic and organic acids, 0and the like. For the protection of such wells, the reagent, eitherundiluted or dissolved in a suitable solvent, is fed down the annulus ofthe well between the casing and producing tubing where it becomescommingled with the fluid in the well and is pumped or flowed from thewell with these fluids, thus contacting the inner wall of the casing,the outer and inner wall of tubing, and the inner surface of allwell-head fittings, connections and flow lines handling the corrosivefluid.

Where the inhibitor composition is a liquid, it is conventionally fedinto the well annulus by means of a motor driven chemical injector pump,or it may be dumped periodically (e.g., once every day or two) into theannulus by means of a so-called boll weevil device or similararrangement. Where the inhibitor is a solid, it is dropped into the wellas a solid lump or stick, blown in as a powder with gas, or it may bewashed in with a small stream'of the well fluids or other liquid. .Wherethere is gas pressure on the casing, it is necessary, of course, toemploy any of these treating methods through 13 a pressure equalizingchamber equipped to allow introduction of reagent into the chamber,equalization of pressure between chamber and casing, and travel of reagent from changer to well casing.

Occasionally, oil and gas wells are completed in such a manner thatthere is no opening between the annulus and the bottom of the tubing orpump. This results, for example, when the tubing is surrounded at somepoint by a packing held by the casing or earth formation below thecasing. In such wellsthe reagent may be introduced into the tubingthrough a pressure equalizing vessel, after stopping the flow of fluids.After being so treated, the well should be left closed in for a periodof time sufiicient to permit the reagent to drop to the bottom of thewell.

For injection into the well annulus, the corrosion inhibitor is usuallyemployed as a solution in a suitable solvent, such as mineral oil,rnethylethyl ketone, xylene, kerosene, or even Water. The selection ofsolvent will depend much upon the exact reagent being used and itssolubility characteristics. It is also generally desirable to employ asolvent which will yield a solution of low freezing point, so as toobviate the necessity of heating the solution and injection equipmentduring winter use.

For treating wells with packed-E tubing, the use of solid stick-s orplugs of inhibitor is especially convenient. These are prepared byblending the inhibitor with a mineral wax, asphalt or resin in aproportion suflicient to give a moderately hard and high-melting solidwhich can be handled and fed into the well conveniently.

The amount of corrosion preventive agent required in our process variesWith the corrosiveness of the system, but where a continuous orsemi-continuous treating procedure is carried out as described above,the addition of reagent in the proportion of from parts per million to2000 parts per million or more parts of corrosive fluid will generallyprovide protection.

These corrosion inhibitors can be used in combination wit-h otherwell-known corrosion inhibitors, for example, the cyclic amidinestructures, the amido cyclic amidine structures, and the amino cyclicamidine structures, as disclosed in the Blair and Gross Reissue PatentNo. 23,227. When the herein described products are mixed with corrosioninhibitors of the conventional type in the ratio of one-to-three,one-to-one, three-to-one, or the like, in numerous instances theeffectiveness of the corrosion inhibitor thus obtained is oftensignificantly greater than the use of either one alone.

They can also be employed as film-forming corrosion inhibitor inconjunction with the aldehyde sulfoxylate compositions described andclaimed in application S.N. 845,325, filed October 9, 1959, now U.S.Patent No. 3,042,609.

As pointed out previously, the addition of corrosion inhibitors,particularly in the form of a solution by means of a metering pump orthe like, is common practice. The particular corrosion inhibitors hereindescribed are applied in the same manner as other corrosion inhibitorsintended fo use for the same purpose. For sake of brevity, as to the useof the corrosion inhibitor and its solution in a suitable solvent suchas mineral oil, methyl ethyl ketone, xylene, kerosene, high boilingaromatic solvent, or even water. i

The molar ratios of cyclic amidine to cycloaliphatic amine can varyWidely depending upon the p-articular species employed, the particularcorrosive system, etc. provided an effective ratio is employed.Illustrative ratios range from about 1 to 1:50, such as from about 20:1to 1:20, for example from about 1:5 to 5:1, but preferably about 1:3 to3:1 'withan optimum of 1.2.

The moles of sulfonic acid employed can also vary widely, provided aneffective amount is employed. Il- .lustrative amounts include the numberof moles necessary to neutralize about 10 to 100 mole percent, such as.30- for example 30-70%, but preferably 30-50 mole percent of the totalbasicity of the cyclic amidine-cycloaliphatic amine mixture, i.e. thenumber of moles of sulfonic acid required for 10% to full neutrality.

The testemployed in evaluating corrosion inhibitors is the copper iondisplacement test described in the application S.N. 695,233, now U.S.Patent No. 3,110,567. In general, it is carried out in the followingmanner:

The test is run by immersing one inch square, sand blasted couponsprepared from 0.006 in. thick shim stock in brine from the corrosivesource for five minutes. The coupons are then transferred without dryingto a solution of a known concentration of the inhibitor in the oil fromthe corrosive source where they are allowed to remain for an additionalfive minutes. The coupons are then transferred to a 10 percent solutionof copper sulfate where they are allowed to remain for 30 seconds. Blankdeterminations are made in the same manner but omitting the inhibitor.The lowest concentration of inhibitor required to prevent the plating ofcopper is taken as the criterion for a pass.

In the following tests a compound is satisfactory if it has a ratingof 1. A rating of 1 indicates that 0-10% of the coupon is copper plated;2, 10-20% of the coupon is copper plated; 3, 20-30% copper plated, 4,30-40% copper plated, 5, 40-50%, 6, 50-60%, etc.

The compositions shown in Table VI are effective corrosion inhibitors.

The composition of Example 1e when actually tested in the field on eightdilferent wells produced the following data:

Table VII FIELD CORROSION TESTS Ex. Compound Well #1 Well #2 Well #3Well #4 Well #5 Well #6 Well #7 Well #8 1f A 3 at 1,400 3 at; 1,200 5 at1,400 3 at 1,600 2 at 1,400 2 at 1,400 2 at 1,800 2 at 1,600 p.p.m.p.p.m. p.p.m. p.p.m. .p.m. .m. .m. .m. 2f 13-. 3 at 1,200 3 at 1,200 1at; 1,400 6 at 1,400 p p p 6 7 1,800 3 2 1,600 p.p.m. p.p.m. p.p.m.p.p.m. p.p.m. p.p.m. 3f C- 1 at 800 1 at 1,000 l at 1,000 1 at 1,200 1at 1,000 1 at 1,400 1 at 1,400 1 at 1,400 p.p.m. p.p.m. p.p.m. p.p.m.p.p.m. p.p.m. p.p.m. p.p.m.

Compound A: N NCH:OH2OH C u sa a. well known corrosion inhibitor ICompound B: N NOHz HzNHi i Un aa a well known corrosion inhibitorCompound C=Ex. 1e.

The ratio employed in Example 12 is the optimum ratio (i.e.1:2:2).

Having thus described my invention, what I claim as new and desire toobtain by Letters Patent is:

1. A corrosion inhibiting composition consisting essentially of ahydroxyaliphatic imidazoline, a cyclohexyl amine and naphthalenesulfonic acid, the molar ratio of said imidazoline to said amine to saidsulfonic acid being 1:2:2.

2. A corrosion inhibiting composition consisting essentially of al-hydroxyalkyl imidazoline, cyclohexyl amine and naphthalene sultonicacid, the molar ratio of said imidazoline to said amine to said sulfonicacid being 1:2:2.

3. A corrosion inhibiting composition consisting essentially of (1) I as(2) cyclohexyl amine, and (3) naphthalene sulfonic acid, the molar ratioof (l) to (2) to (3) being 1:2:2.

4. The process of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in producing oil and gas wellscomprising introducing into the well a corrosion inhibiting compositionconsisting essentially of a hydroxyaliphatic imidazoline, a cyclohexylamine and naphthalene sulfonic acid, the molar ratio of said imidazolineto'said amine to said sulfonic acid being 5. The process of inhibitingcorrosion of ferrous metals exposed to corrosive agents normally presentin producing oil and gas wells comprising introducing into the well acorrosion inhibiting composition consisting essentially of al-hydroxyalkyl imidazoline, cyclohexyl amine and naphthalene sulfonicacid, the molar ratio of said imidazoline to said amine .to saidsulfonic acid being 1:2:2.

6. The process of inhibiting corrosion of ferrous metals exposed tocorrosive agents normally present in producing oil and gas Wellscomprising introducing into the well a corrosion inhibiting compositionconsisting essentially of (l) CHzCHzOH 0 171123 (2) cyclohexyl amine,and (3) naphthalene sulfonic acid, the molar ratio of (1) .to (2) to (3)being 1:2:2.

References Cited by the Examiner UNITED STATES PATENTS 2,468,163 4/49Blair et al. 252-8.55 2,828,259 3/58 Wirtel et a1. 252-855 2,856,35810/58 Riggs 2528.55 2,882,227 4/59 Lindberg 252-855 2,888,399 5/59Vs/irtel et al. 252-8.55 2,940,927 6/60 Hughes 2528.55 3,025,239 3/62Sheldahl 252391 JULIUS GREENWALD, Primary Examiner.

1. A CORROSION INHIBITING COMPOSITION CONSISTING ESSENTIALLY OF AHYDROXYALIPHATIC IMIDAZOLINE, A CYCLOHEXYL AMINE AND NAPHTHALENESULFONIC ACID, THE MOLAR RATIO OF SAID IMIDAZOLINE TO SAID AMINE TO SAIDSULFONIC ACID BEING 1:2:2.